Detection of road conditions using a beam from an external system i.e. gps, dbs

ABSTRACT

Device for scanning radiation-based surface state recognition, especially of roads.  
     The invention relates to a device for scanning radiation-based recognition of the surface state of earth surface regions with receivers for receiving at least one state information scanning radiation component reflected from the scanned earth surface region and with evaluation resources for determining the surface state of the scanned earth surface region by evaluation of the scanning radiation received.  
     In accordance with the invention, the scanning radiation is formed by the useful signal radiation of a foreign system and/or is generated by one or more satellites.  
     Use for example for recognition of the surface state with respect to paving type and paving condition of thoroughfares.

[0001] The invention relates to a device for scanning radiation-based recognition of the state of the ground surface, especially of thorofare areas, according to the preamble of claim 1.

[0002] In published patent specifications U.S. Pat. No. 04,653,316, U.S. Pat. No. 4,690,553, U.S. Pat. No. 5,446,461 and U.S. Pat. No. 5,497,100, devices of this type for recognition of the state of the surface of roads are described which are all designed as “active” systems, by which it is to be understood that they include a scanning radiation transmitter specially provided for this purpose which generates the scanning radiation used, at least one part of which is directed toward the road area to be monitored. Visible light, for example, from a laser, or infrared radiation or another electromagnetic radiation, for example, is used as scanning radiation. At least one scanning radiation component reflected from the scanned road region which contains the information on the state of the surface is recorded through suitable receivers and fed to evaluating resources which subject this state information scanning radiation component to a suitable evaluation in order to draw an inference on the surface condition of the scanned road region. The evaluation can entail, according to system design, a comparison of several scanning radiation components directed toward the street region monitored and/or a comparison of one or more such reflected scanning radiation components with an associated reference scanning radiation which reaches the receiver from the scanning radiation transmitter without prior reflection on the road area monitored. The recognition of the condition of the road surface in particular serves to establish whether the street is dry or wet or whether it is covered by snow or ice.

[0003] As an alternative to the active system design, a “passive” system of a device of the type mentioned at the beginning is described in published patent specification U.S. Pat. No. 5,521,594, whereby a system design is to be understood which utilizes radiation present in any case for other reasons as scanning radiation and therefore manages without a scanning radiation transmitter to be provided specially for this purpose. The device there, which inevitably must be installed in a motor vehicle, uses ultrasound spurious emission, that is ultrasound noises which are generated during travel by a motor vehicle tire and are clearly heightened with a wet road in contrast with a dry road. Passive systems generally have in comparison with active systems the advantage that the expenditure for an independent scanning radiation transmitter is unnecessary, and moreover no additional radiation is introduced into the in any case mostly strongly radiation-stressed environment. The use of ultrasound noise generated on the part of tires is nonetheless basically restricted to differentiating between dry and wet roads, and above all to systems installed on the part of the motor vehicle.

[0004] Underlying the invention as a technical problem is readying a device of the type mentioned at the beginning with which the state of the surface of thorofare areas and other ground surface regions can be recognized with a relatively small expenditure reliably and exactly, especially passing into what type of paving is present and/or whether the scanned surface is wet or dry or is covered by ice, snow, sand or the like.

[0005] The invention solves this problem by furnishing a device with the features of claims 1 or 2.

[0006] With the device according to claim 1, the scanning radiation is characteristically formed from the useful signal radiation of a foreign system. By useful signal radiation is here to be understood a radiation which functions as a useful signal of the foreign system, whereby by foreign system, any arbitrary other system outside the surface state recognition device is meant. The device according to claim 1 consequently makes use of a useful signal radiation produced in any case by the foreign system in order introduce it as scanning radiation. In other words, the useful signal radiation is doubly used, on the one hand as a useful signal for the foreign system and on the other as scanning radiation for surface state recognition. The device according to claim 1 correspondingly forms a passive system in the sense defined above with the additional advantage that it uses a useful signal radiation of a foreign system as scanning radiation which is in any case generated by the foreign system. In contrast to using a spurious emission within the framework of such a passive system design, the use of a useful signal radiation has the advantage that the latter will generally be very dependably available since it is to be sure required by the foreign system for its useful signals.

[0007] The device according to claim 2 is distinguished by the fact that the scanning radiation is generated from one or more radiation transmitters arranged satellite side. This makes possible a correspondingly large area use of the scanning radiation on the ground surface and therewith, for example, a recognition of the road surface conditions over spacious road traffic networks without having to install a scanning radiation transmitter in every motor vehicle using the traffic network. This measure of the invention can if needed be combined with that of claim 1 if the radiation emitted satellite side at the same time forms a useful signal radiation of a satellite-based foreign system.

[0008] The latter exists in a refinement of the according to claim 3, in that the scanning radiation is formed by the radar or radio wave beaming of a satellite-supported locating system, such as GPS (Global Positioning System), or a satellite-supported radio or transmission system, such as DBS (Direct Broadcasting System).

[0009] In a refinement of the device of the invention according to claim 4, the evaluation of the received scanning radiation takes an associated reference scanning radiation component likewise received, that is, a scanning radiation component which is not reflected from the monitored ground surface region in addition to the scanning radiation component radiated from the monitored ground surface region, and which is therefore suitable as a reference for comparison with the scanning radiation component reflected from this region which contains information on the condition of the surface. Such a comparison with a reference scanning radiation component can improve the quality of surface state recognition.

[0010] In a refinement of the invention according to claim 5, the reflected state information scanning radiation component and if need be the additional scanning radiation component or components received are evaluated by the evaluation apparatus at least with respect to amplitude, phase and/or polarization state, whereby the simultaneous use of two or all three of these evaluation criteria can improve the quality of surface state recognition.

[0011] In a refinement of the invention according to claim 6, the evaluation devices contain suitable classification resources which enable a classification of the surface state into several different, specifiable types, for example a classification of the condition of a scanned street paving into various paving types, such as concrete, sand, fine stone (such as asphalt, tar and ballast) and coarse stone (such as brick and paving stones).

[0012] Advantageous embodiments of the invention are represented in the drawings and are described below, wherein:

[0013]FIG. 1 Gives a schematic representation of a part of a device for recognizing the surface state of thorofare regions,

[0014]FIG. 2 Provides a block diagram of a receiver and evaluation element of the device in accordance with FIG. 1,

[0015]FIG. 3 Shows a block diagram of the receiver element of FIG. 2 and

[0016]FIG. 4 Depicts a block diagram of a signal processing element for feature derivation within the evaluation element of FIG. 2.

[0017] The embodiment represented in the drawings and subsequently explained in greater detail represents a device for scanning radiation-based recognition of the state of the surface of thorofare regions, which in particular uses radar or radio wave radiation of a GPS or DBS. The surface state recognition system uses useful signal radiation for this which is emitted from appropriate GPS or DBS satellites primarily to fulfill the locating or radio or remote data transmission function of the GPS or DBS foreign system.

[0018] As represented by way of example in FIG. 1 on the basis of several participating satellites 1, the useful radiation is emitted from satellites 1 as scanning radiation for surface state recognition such that three different useful signal radiation components are received as corresponding scanning radiation components and evaluated by the respective antenna unit 2. In particular, a first scanning radiation component 4 a with a first polarization state reflected from the monitored road region 3, a second scanning radiation component 4 b reflected from the monitored road region 3 with a second polarization state, and a reference scanning radiation component 4 c coming directly from the satellites 1 without prior reflection on the monitored road region 3 are received and evaluated. Preferably, GPS as well as DBS useful radiation is used as a scanning radiation for surface state recognition in order to obtain an especially high quality for judging the surface condition.

[0019] Since GPS and DBS or TV satellites operate around the globe and are available, the road surface state of traffic networks can be recognized worldwide with the present device with standardized receiver and evaluation parts which are tuned to the standardized GPS or DBS useful radiation without adaptations to different national standards or regulations being necessary. By evaluating the useful signals of at least four of the participating satellites 1, the respective time and place coordinates can be determined.

[0020] In the example of FIG. 1, several antenna units 2 are in any given case mounted on beacons 5 arranged stationarily distributed over the road traffic network which can enter, in a traditional manner not shown in greater detail, into communication connection with motor vehicles 6 passing by. The motor vehicles 6 are then outfitted with the associated evaluation element in order to evaluate the scanning radiation data recorded by the antenna unit 2 for recognition of the road surface condition. Alternatively, a street-side, stationary arrangement of evaluation elements and associated indicator units can be provided through which then the local street surface state can be indicated to passing motor vehicles, for example, on existing traffic information beacons or bridges together with other traffic information. In a further alternative, antenna and evaluation element can be arranged completely on the part of the vehicle.

[0021]FIG. 2 shows in a schematic overview the crude structure of the passive device for recognizing street surface conditions. As is apparent form it, a digitalization stage 8 is joined to an input stage 7 which encloses the antenna element and a high frequency front end, a digitalizing stage 8 to which a feature extraction stage 9 is connected downstream in series. The output information of the feature extraction stage 9 is fed into a classification stage 10 in which it is compared with model condition data for the purpose of classification which are deposited in an associated model memory 11, and indeed in the form of a specifiable number of different model states 12 a, 12 b, 12 c, 12 d, such as concrete, fine stone (for example, in the form of asphalt, tar or ballast), coarse stone (for example, in the form of bricks or pavement stone) and sand.

[0022]FIG. 3 shows in greater detail the antenna and HF front end element of FIG. 2 which is designed for receiving of DBS signals in the so-called C band, that means in the region of 4000 MHz as well as GPS signals in the so-called L band at 1575.42 MHz. Overall, the receiver stage contains three parallel receiving channels for the three different recorded scanning radiation components 4 a, 4 b, 4 c. The radiation components 4 a, 4 b, 4 c received are then converted down evenly in the three channels in several steps. In particular, the DBS signal components of the three scanning radiation components 4 a, 4 b, 4 c are mixed down to 4 MHz in three steps. The GPS signal components are likewise mixed down to a frequency of 4 MHz, whereby already a twofold downward conversion suffices owing to the low input frequency.

[0023] For this, the input signal in the respective channel is first passed through a bandpass filter 14 with a band width of 60 MHz for this in a first stage 13, thereafter amplified in an amplifier 15 with 50 dB and subsequently mixed in a local oscillator 16 with a radio frequency signal with a frequency of 5575.42 MHz additionally fed to this, whereby this processing stage 13 in particular concerns the DBS signal component. In a next stage, the signal coming from the local oscillator 16 is led over a bandpass filter 17 with a band width of 4 MHz in order to obtain a center frequency of 1575.42 MHz as it exists for the GPS signal component from the start. From this point on, the DBS and the GPS signal components are further processed in the same manner.

[0024] This further processing first of all entails an amplification in an amplifier 18 with 75 dB, after which the amplified signal with a frequency of 1575.42 MHz is mixed in a local oscillator 19 with a signal fed to this in addition at a frequency of 1505.42 MHz. The mixed signal is passed over a bandpass filter 20 with a bandwidth of 2 MHz, and subsequently reamplified in an amplifier 21 with 35 dB. The amplified signal then possesses a center frequency of 70 MHz and a bandwidth of 2 MHz. In an additional local oscillator 22, it is mixed with a signal fed to it in addition at a frequency of 66 MHz, after which it is passed through a bandpass filter 23 with a bandwidth of 2 MHz and subsequently amplified in a further amplifier 24 with 20 dB.

[0025] The three parallel resulting signals with the desired central frequency of 4 MHz are then subsequently fed to the digitalization stage 8 which contains an A/D transducer as an essential element. The three parallel signals with a central frequency of 4 MHz and bandwidth of 2 MHz are digitalized in the digitalization stage 8 to 5 MHz. In the subsequent feature extraction stage 9, see FIG. 2, the three digitalized signals are processed further through a suitably designed computer with respect to feature extraction.

[0026]FIG. 4 shows a suitable construction of the feature extraction stage 9. As is apparent form it, the digitized signals 25 a, 25 b, 25 c, which correspond to the three different scanning radiation components 4 a, 4 b, 4 c received (see FIG. 1), are processed on the basis of the three channels of the digitalization stage with respect to the derivation of the features relevant for the later classification in that first of all, in a correlation stage 26, each of the three signals 25, 25 b, 25 c, that is, the direct signal D and the two “reflected” signals R1, R2, which contain state information on the scanned surface, are subjected to an auto-correlation 26 a, and the two reflected signals R1, R2 are correlated parallel thereto in any given case with the direct signal D. An FFT stage 27 is joined in any given case to the corresponding five output channels of correlation stage 26 in which a 1000 point FFT (Fast Fourier Transformation) is conducted to obtain a performance spectrum. In a subsequent smoothing stage 28, each of the 1000 dimensional five individual vectors are smoothed in the spectral range into a 20 dimensional vector in that the mean for blocks of in any given case 500 units is formed. Here the auto-correlation spectra of the direct and reflected signals are thus calculated. Three 20 dimensional vectors result from this. The cross correlation spectra are computed and smoothed from which two complex 20 dimensional vectors each result. From these spectra, a 140 dimensional feature vector 29 consequently arises which is fed to the classification stage 10.

[0027] In classification stage 10, a classifying processing of the information contained in feature vector 19 on the surface condition of the scanned road region with respect to road paving types takes place, that is, a decision on to which of several specified road paving types, that is model states 12 a to 12 d, as they are deposited in model memory 11, best corresponds to the recorded and previously processed surface condition data. Classification stage 10 can, for example, contain two classifiers for this, namely a statistical classifier and a neuronal classifier. A conventional type which rests on a Mahalanobis distance determination can especially be used as a statistical classifier. For further details on Mahalanobis distance determination, it is possible to refer to the literature. See, for example, R. O. Duda and P. E. Hardt, Pattern Classification and Scene Analysis, Wiley Interscience, John Wiley, 1973. The neuronal classifier can consist of a, for example, three layer perceptron which is suitably trained with an inverse processing algorithm. Reference can likewise be made to the literature in this regard. See, for example, the textbook D. E. Rumelhart et al., Learning Internal Representations by Error Propagation, Chapter 8 in Parallel Distributed Processing, Volume 1, Cambridge, MIT Press. The two classifiers are constructed with the aid of training data which consist of a suitable set of feature vectors corresponding to various surface classes, that is, model states.

[0028] In operation, the evaluation element then first of all performs with its classification stage an assessment on which paving type the street area just scanned has, that is, whether it is a matter of a stretch with asphalt, tar, sand, ballast, paving bricks etc., and secondly makes a judgment on the momentary surface grip traction condition, that is, whether the road region scanned is dry or whether there is moisture or whether it is covered with ice or snow. The data evaluation for this surface condition assessment corresponds to the one as it is known from customary active systems for surface condition recognition, and therefore requires no more detailed explanation here. The signal evaluation takes place with respect to amplitude, that is, the signal output, as well as with respect to the phase and polarization state for a high recognition exactitude. Alternatively, an evaluation only of amplitude or only of amplitude and polarization or phase can suffice if, for example, very many different road surface states must be recognized, or a restricted exactitude of classification of the same suffices.

[0029] The embodiment described above makes clear that, through the invention, a device for recognition of the surface condition of thoroughfares and other earth surface regions is advantageously created which uses a useful signal radiation and/or a radiation emitted from satellites present in any case as scanning radiation. It is in this way practically usable worldwide over a large area without greater modifications in a uniform manner, and does not unconditionally require its own scanning radiation generation apparatus. In this way, the additional introduction of radiation into the environment is avoided, just like the expenditure of active systems going along with the radiation generators to be created in addition. 

Patent claims:
 1. Device for scanning radiation-based recognition of the surface condition of ground surface regions, especially of thorofare regions, with Receivers (7) for receiving at least one state information scanning radiation component (4 a, 4 b) reflected from a scanned ground surface region (3) and Evaluation resources (8, 9, 10) for determining the surface state of the scanned earth surface region by evaluation of the scanning radiation received containing at least the state information scanning radiation component, characterized in that The scanning radiation (4 a, 4 b, 4 c) is formed from useful signal radiation of a foreign system.
 2. Device for scanning radiation-based recognition of the surface condition of ground surface regions, especially according to claim 1, with Receivers (7) for receiving at least one state information scanning radiation component (4 a, 4 b) reflected from a scanned ground surface region (3) and Evaluation resources (8, 9, 10) for determining the surface state of the scanned earth surface region by evaluation of the scanning radiation received containing at least the state information scanning radiation component, characterized in that It contains one or more satellites (1) for generating the scanning radiation (4 a, 4 b, 4 c).
 3. Device according to claim 1 or 2, further characterized in that the scanning radiation is made of useful signal radiation of a locating system (GPS) and/or a radio or television transmitting system (DBS).
 4. Device according to one of claims 1 to 3, further characterized in that the received and evaluated scanning radiation includes in addition a reference scanning radiation component (4 c) not reflected from the scanned earth surface region.
 5. Device according to one of claims 1 to 4, further characterized in that the evaluation resources (8, 9, 10) evaluate the received scanning radiation with respect to amplitude, polarization and/or phase.
 6. Device according to one of claims 1 to 5, further characterized in that the evaluation resources contain a classification stage which classifies the surface condition of the scanned earth surface region in accordance with several specifiable model conditions (12 a to 12 b). 